When shoes, in particular sports shoes, are manufactured, two objectives are to provide a good grip on the ground and to sufficiently cushion the ground reaction forces arising during the step cycle, in order to reduce strain on the muscles and the bones. In traditional shoe manufacturing, the first objective is addressed by the outsole: whereas, for cushioning, a midsole is typically arranged above the outsole. In shoes subjected to greater mechanical loads, the midsole is typically manufactured from continuously foamed ethylene vinyl acetate (EVA).
Detailed research of the biomechanics of a foot during running has shown, however, that a homogeneously shaped midsole is not well suited for the complex processes occurring during the step cycle. The course of motion from ground contact with the heel until push-off with the toe part is a three-dimensional process including a multitude of complex rotating movements of the foot from the lateral side to the medial side and back.
In the past, to selectively influence this course of motion, different support elements have been integrated into the foamed midsole with different material properties that, for example, selectively avoid supination or excessive pronation of the wearer of the shoe. This applies in particular to the forefoot part of the sole, which determines the rolling-off and the push-off properties, and also to the heel part of the sole, which determines the reaction of the shoe during initial ground contact.
Although some progress has been made in the biomechanical control of the step cycle, these developments have a series of disadvantages. For example, the addition of specific support elements to the foamed midsole substantially increases the weight of the shoe, which becomes particularly apparent and disadvantageous with running shoes. Further, the integration of the support elements substantially increases the production costs of the sole, since each of these elements must be securely connected to the surrounding midsole by, for example, cementing, fusing, etc. during manufacture of the shoe.
The described approach of the prior art hinders an easy and cost-efficient modification of the biomechanical properties of a midsole, since each change of the support elements, either with respect to their material or their shape, requires a complete redesign of the midsole. It is not possible to quickly adapt the shoe to new results of biomechanical research or to the changing requirements of a new kind of sport activity.
It is, therefore, an object of the present invention to provide a shoe sole that can be adapted to provide increased support for an arch region of a foot and a high degree of flexibility in a forefoot region, either for cushioning or elastic energy storage.